Combinatorics - practice problems - page 3 of 54
Number of problems found: 1079
- 3 sigma
Students' performance scores in a statistic test have a mean of 70 and a standard deviation of 4.0. The scores obtained can be modeled by a normal distribution. Find the probability that the score of a randomly selected student is i. more than 80 marks ii - Containers
One in eight containers is temporarily misplaced. A random sample of 12 containers is selected. What is the probability that 6 of these containers will be temporarily misplaced? - Bulb life
Tests show that the lives of light bulbs are normally distributed with a mean of 750 hours and a standard deviation of 75 hours. Find the probability that a randomly selected light bulb will last between 675 and 900 hours. - 3 pens
3 pens are to be taken from a bunch of 100 pens.If 10 pens are defective, find probability of getting all good pens. - And or logic
If A and B are events with P(A)=0.3, P(A OR B)=0.76, and P(A AND B)=0.04, find P(B). Enter your answer in decimal form, rounded to one place. - And - or probability rules
Given P(A)=0.4, P(B)=0.56, and P(A and B)=0.274, find the value of P(A or B), rounding, if necessary. - The profit 3
An investment's profit (or loss) is normally distributed with a mean of $11,200 and a standard deviation of $8,250. What is the probability of a loss rather than a profit? - Triangles - segments
How many triangles can be formed with segments measuring one and 2/3 mm one 3/4 mm and 2 1/2 mm - Diagonals
What is the number of diagonals of a decagon? - Ekene and Amina
The probability that Ekene will be alive in 5 years' time is 3/4, and the probability that his wife Amina will be alive in 5 years' time is 2/5. Find the probability that in 5 years' time: a) both of them will be alive b) only Ekene will be alive - Fish service
According to a report by the U. S. Fish and Wildlife Service, the mean length of six-year-old rainbow trout in the Arolik River in Alaska = 484.6 millimeters with a standard deviation = 31.2 millimeters. Assume these lengths are normally distributed. What - Family survey A total of 160 families with 4 children each were surveyed with the following results. Boys; 4; 3; 2; 1; 0 Girls ; 0; 1; 2; 3; 4 Families; 7; 50; 55; 32; 16 Let the probability of picking a boy or a girl be 1/2. Let P=boy, Q=girl. What is the probability
- Repairs
A small repair shop orders parts for its repairs. Its supplier claims that only 2% of its parts are defective. In order of 500 parts, an employee takes a sample of 100 parts. Determine the likelihood that the employee finds three or more parts are defecti - Drunken drivers
40% of drivers driving between 11 pm and 5 am are drunken drivers. In a random sample of 20 drivers driving between 11 pm and 5 am, find the probability that: A) Exactly 12 will be drunken drivers B) At least 7 will be drunken drivers C) At most 5 will be - A random 2
A random sample of 40 families has an average water consumption of 29 cubic meters per month, with a sample standard deviation of 8 cubic meters. Give the 90% confidence interval for the mean usage of water per month. - Defect rate
A manufacturing machine has a 3% defect rate. If 9 items are chosen randomly, what is the probability that at least one will have a defect? - A disease A disease affects 10% of the individuals in a population, and a sample of 100 people was selected from the population. What is the probability of finding the disease in at least 15 people?
- Morse code 2
We have two characters, a dot and a comma. How many two-element and how many three-element characters can be created with repetition? - In class 24
There are a total of 16 students in the class, a quarter of whom are girls. We randomly select a team of five. Determine the probability that the team will have: a) at least 4 girls. b) at most 1 girl. c) no girls. - Christmas 4
There are only 3 packages left under the tree - two for Julka and one for Zuzka. Julka took two at once. What is the probability that both belong to her?
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